The present invention relates to a MOS type solid state image sensor for use in a digital camera and the like.
FIG. 17 shows an example of a conventional solid state image sensor composed of MOS transistors. This solid state image sensor includes a photosensitive region 14 in which a plurality of amplifying unit pixels are two-dimensionally arranged on a semiconductor substrate, and each of the unit pixels includes a photodiode (PD) 1, a read transistor 2, a floating diffusion (FD) portion, a reset transistor 3, a detect transistor 4 and an address transistor 5. The solid state image sensor further includes signal lines 6, drain lines 7, read gate lines 8, reset gate lines 9, address gate lines 10, a vertical shift register 12 for selecting a row of pixels, a horizontal shift register 13 for selecting a column of pixels, and a timing generation circuit 11 for supplying necessary pulses to the shift registers 12 and 13.
Signal charge having been subjected to photoelectric conversion by the PD 1 is read by the read transistor 2 to the FD portion which is a storage region for storing the signal charge. The potential of the FD portion is determined according to the amount of charge thus read to the FD portion, so as to change the gate voltage of the detect transistor 4, and if the address transistor 5 is selected, a signal voltage is taken out onto the signal line 6.
Although the signal voltage is taken out onto each corresponding signal line 6 in the conventional solid state image sensor of FIG. 17, power pulses are simultaneously supplied through the drain lines 7 to all the two-dimensionally arranged plural amplifying unit pixels. Accordingly, this conventional technique is disadvantageous in consuming large power.